# coding: gb2312
# Copyright (C), 2013-2060, NetEase.
# Author: lixin
# Date: 2013-5-17
# Description: 
class Subject:  

    def register(self, observer):  
        pass  
  
    def deregister(self, observer):  
        pass  
  
    def notify_observers(self):  
        pass  
  
class Observer:  
    def update(self, temperature, humidity, pressure):  
        pass  
  
class DisplayElement:  
    def display(self):  
        pass 